This invention relates to endoscopy and to materials suitable for use as everting liners for emplacing an instrument, such as an endoscope or a colonoscope, into the body.
Colon cancer is the most common visceral malignancy in the United States. There is substantial evidence that nearly all colonic malignancy has its origin in previously benign polyps, and that most colon cancer could be prevented if these polyps could be detected and removed while they are still benign.
A diagnostic procedure generally employed when malignancy of the large intestine is suspected is colonoscopy, in which the interior of the colon is examined by means of an elongated flexible fiber optic endoscope, known generally as a colonoscope.
A colonoscope for use in transanal colonoscopy is an instrument that typically includes a flexible tube sufficiently long that, when fully inserted into the colon through the anal canal, it can extend through the full length of the colon so that its proximal (inward) end reaches to the cecum. Colonoscopes can be nearly six feet long, and can have a diameter as little as about one-half inch. The proximal tip, that is, the portion about six inches long at the proximal end, is typically maneuverable by manipulation of controls at the other (distal) end. Incorporated in the tip are a light source and fiber optics for illumination and visual observation; and tools for carrying out irrigation, suction, and surgical procedures such as polyp removal.
The procedure most commonly followed for a colonoscopic examination is first to insert the colonoscope by way of the anal canal in a proximal direction into the colon as far as desired, making only a cursory inspection along the way, and then to withdraw the colonoscope distally, while examining the colon more thoroughly, performing biopsies, or removing polyps as appropriate. For an examination of the entire colon, the colonoscope is inserted through the anal opening and the anal canal into the rectum, then advanced through the sigmoid flexure into the descending colon, then from the descending colon through the left colic flexure (the splenic flexure) into the transverse colon, and then from the transverse colon through the right colic flexure (the hepatic flexure) into the ascending colon as far as the caecum. Insertion is effected by maneuvering the colonoscope tip so that it is aimed in the proper direction while (at the distal end) grasping the colonoscope at a point outside the body near the anal opening and pushing inward. The colonoscope is sufficiently stiff that it can be inserted without buckling even when many pounds of pushing force are applied.
Advancing the colonoscope tip within the colon is a difficult procedure, and it can be particularly difficult to advance the instrument through the sharp bends of the colon at the sigmoid flexure and the splenic flexure. As the instrument is worked through these bends the sigmoid colon distends and the pressure of the colonoscope on the colon walls tends to stretch that portion of the colon through which the instrument has already passed rather than advancing the tip further into the colon. In some instances, and particularly when the colon has been irritated or sensitized by the movements of the colonoscope within it, reflex action by the colon wall musculature can cause the colon to constrict around the colonoscope during insertion through these bends, aggravating the tendency of the colon to distend lengthwise. Muscle relaxants used to relax the circumferential colonic musculature can prevent this reflex constriction, but such relaxants can also relax the longitudinal colonic musculature, resulting in still further lengthwise stretching of the colon rather than proximal advancement of the colonoscope tip.
Insertion of the instrument can be uncomfortable for the patient, and the physician inserting the colonoscope may rely to some extent on the patient's complaints as an indication that the instrument has been misdirected. In cases where the procedure is acutely painful, anaesthetics can be used, but they also deprive the physician of the benefit of patient response, and moreover can require postanaesthetic recovery procedures.
Moreover, there is a substantial risk of perforation of the colon by the tip of the colonoscope during insertion, even when performed by surgeons having some experience with the procedure. Although some surgeons have been able, through care and skill, virtually to eliminate the risk of perforation, there exists a finite rate of complications resulting from diagnostic colonoscopy.
Although the inspection itself of the colon, carried out during withdrawal of the instrument, typically takes only about ten minutes' time, insertion of the colonoscope typically takes as much as 50 minutes' time, owing to difficulties in inserting the instrument and because of the care that the physician must take to reduce the likelihood of harm to the patient. Too often the insertion is halted when the tip is at a point far short of the caecum, because a portion of the colon already negotiated by the colonoscope (particularly the sigmoid flexure or the splenic flexure) may constrict tightly upon the colonoscope and prevent further advance, or because the patient cannot tolerate the procedure any further or because the physician is fearful of the danger to the patient, or for some other reason. As a result, the diagnosis is incomplete because a portion of the colon proximally beyond the farthest point reached by the tip escapes examination.
It is known to aid inspection of the inner wall of the colon by everting into the colon a flexible tube which remains generally immobile with respect to the colon wall. An object such as a medical instrument can be drawn into the intestine by the everting tube as the eversion of the tube progresses.